Wind Turbine Wake Merging Descriptions and Quantification

Wind tunnel experiments were performed with three arrangements of model turbines in symmetric and asymmetric configurations. Asymmetric congurations included a single turbine upstream of two evenly spaced turbines and a single turbine downstream of two evenly spaced turbines. Hot wire anemometry was used to measure simultaneously instantaneous velocity signals across eleven spanwise locations at three distances downstream of the last row in the turbine array. Two inflow conditions with turbulence intensities of 4% and 10% were investigated. Arrangement symmetry is found to be a key parameter where the position of the furthest downstream turbine is the dominant factor when considering the downstream velocity field. Consideration of the energy thickness and shape factor revealed the wake region to extend as an energy and momentum deficit beyond the velocity deficit. The energy spectra near regions of wake interaction indicate production of turbulence at scales equivalent to the model rotor radius. In these areas, the flow is highly self-correlated and serves to enhance wake longevity downstream by injecting energy into the system.